1. Field of the Invention
The invention generally relates to the ex vivo generation of T cells for use in adoptive cell transfer (ACT). In particular, the invention relates to a step-wise combination protocol for generating T cells that are resistant to immune suppression, for use in the prevention and treatment of e.g. cancer and infectious disease.
2. Background of the Invention
When a cancerous tumor develops in a patient, the patient's immune system typically responds to the presence of the tumor by generating immune cells [e.g. immune effector cells such as lymphocytes, macrophages, dendritic cells, natural killer cells (NK cells), NKT cells, cytotoxic T lymphocytes (CTLs), etc.] that attack the tumor. However, depending on the characteristics of the tumor, the immune response, and other factors, the response may not be sufficient to completely destroy the cancer cells.
The technique of adoptive cell transfer (ACT, or, alternatively, adoptive immunotherapy, AIT) is used as a cancer treatment to augment an insufficient immune response. The rationale for the use of ACT in treating cancer is based on overcoming the low frequency of endogenous tumor-reactive T cells. For ACT, T cells that have a natural or genetically engineered reactivity to a patient's cancer are generated in vitro by ex vivo activation, expansion, and directed differentiation toward the most effective phenotype(s), and are then transferred back into the cancer patient. For example, autologous T cells that are found with the tumor of a patient, which are already naturally trained to attack the cancerous cells, may be manipulated in this manner. The expanded cytotoxic T cells are then transferred back into the patient where they recognize, attack and (theoretically) eliminate the tumor. Initial studies of adoptive cell transfer, however, revealed that persistence of the transferred cells in vivo was too short to be effective, and that lymphodepletion of the recipient (e.g. by total body radiation) prior to administration, is required to eliminate regulatory T cells (which diminish T cell activity) as well as normal endogenous lymphocytes that compete with the transferred cells for homeostatic cytokines which are necessary for full activity of T cells.
Several groups have shown that ACT directed against melanoma-associated antigens results in objective responses in animal models as well as in some melanoma patients (1, 2). To improve objective responses of ACT, a number of strategies have been developed which include using genetically modified lymphocytes (3), highly effective T cell phenotypes (4) and exposure of the T cells to common gamma-chain cytokines prior to administration (5). However, despite these modifications to ACT protocols, they are still not effective in all cases. One possible explanation is that, unlike animal models, cancer patients usually receive ACT after conventional therapies which could interfere with the efficacy of the donor T cells and be responsible for the variable results observed in patients. No comparative analysis has heretofore been performed to determine whether previous radiation therapy reduces or enhances the anti-tumor efficacy of ACT.
ACT has also been tested against breast cancer both in mouse models of breast cancer and breast cancer patients (6, 7). Unlike melanoma, ACT has never been shown to produce complete protection against breast tumors. Barriers to success include difficulty in the ex vivo expansion of tumor-reactive T cells (8), uncertainty as to the most relevant antigens, a lack of consensus as to the appropriate origin of the T cells to be used for expansion as well as phenotypic distribution of the most effective T cells, tumor stroma which act as a major barrier which prevents penetration of T cells into the solid tumor (10), and the presence of myeloid-derived suppressor cells (MDSC) in cancer patients during pre-malignant carcinogenesis which can abrogate anti-tumor efficacy of ACT (7, 9). Tumor-bearing animals and cancer patients have increased MDSCs due to the presence of the cancer, and MDSCs suppress anti-tumor T cells. As a result, in many cases, patients' own immune system fails to protect them against cancers. In addition, the presence of MDSCs usually results in the failure or attenuation of immunotherapy.
Some infectious disease agents also have the ability to evade immune clearance by suppressing the immune system. For example, infection with influenza A virus (IAV) results in the expansion of myeloid-derived suppressor cells (MDSC), which in turn suppresses IAV-specific immune responses (De Santo C, Salio M, Masri S H, Lee L Y, Dong T, Speak A O, Porubsky S, Booth S, Veerapen N, Besra G S, Gröne H J, Platt F M, Zambon M, Cerundolo V. Invariant NKT cells reduce the immunosuppressive activity of influenza A virus-induced myeloid-derived suppressor cells in mice and humans. J Clin Invest. 2008 December; 118(12):4036-48).
There is an ongoing need to investigate these factors and to modulate ACT protocols in order to achieve higher levels of success in tumor eradication for all types of cancer, and for the treatment of infectious diseases. In particular, there is a great need to develop an effective ACT protocol for the treatment of breast cancer.